1. Field of the Invention
This invention relates to a sewing data forming method and device for so-called electronic sewing machines equipped with an X-Y table which is driven by needle position data.
2. Description of the Related Art
Among industrial electronic sewing machines, an automatic sewing machine which automatically sews a material along a desired sewing pattern by driving either the material or the needle according to sewing information preprogrammed and stored in a memory unit is in practical use. The above-mentioned sewing information is stored in a storage medium of the memory unit, and sewing with different sewing patterns can be performed simply by replacing this storage medium. The storage medium is generally made of semiconductor memories or magnetic cards, and contains control information for controlling the movement of the sewing machine according to the operating procedures. The control information usually consists of information regarding relative offsets between the needle and the material for every stitch that forms the sewing pattern, a sewing speed, and a control command for other movements. The control information for a set of sewing pattern is formed as a collection of control commands for every stitch.
Accordingly, in order to perform the automatic sewing operation according to the desired sewing pattern using this automatic sewing machine, it is necessary to form control data corresponding to the sewing pattern and store it in a predetermined storage medium.
FIG. 6 is a perspective view showing a sewing data forming device for the conventional sewing machine disclosed in Japanese Patent Unexamined Publication No. 60-148582. The device is provided with a menu section (11) for inputting and a tablet digitizer (10) having a pattern input section (13), both on the front thereof. The operation of the device will next be explained with reference to the block diagram shown in FIG. 5.
By drawing a desired sewing pattern on the tablet digitizer (10) using a cursor (12), a CPU (14) is caused to control so that the drawn sewing pattern is written as a sewing pattern data signal from a PROM write circuit (16) through a gate (44) to a PROM which forms the desired pattern data. The PROM to which the pattern has been written is then loaded to a sewing machine control unit (40) as a PROM cassette (42) to drive a sewing machine (38). The PROM is inserted into a PROM socket (18) shown in FIG. 6. Various modes and operating procedures at the time of input are displayed as I/O data on an LED display panel (20) through the gate (44). A program by which the input data is written by the CPU (14) to the PROM from the tablet digitizer (10) through a gate (48) is stored in a system program ROM (22). Thus, the CPU (14) performs a processing according to this program. The input data from the tablet digitizer (10) is temporarily stored in a data memory RAM (24) composed of a RAM, and the memory values are stored therein as relative value data which indicate X and Y coordinate data of the tablet digitizer (10) in terms of X, Y stitch offsets. A monitor display CRT (26) is also provided to monitor data when input data of the tablet digitizer (10) is written to the PROM. The CPU also converts the data in the data memory RAM (24) into graphic data, and causes the graphic data thus converted to be stored in a graphic data memory RAM (28) through a gate (32). The data thus stored are converted from digital values into analog values (voltage) by D/A converters (34) and (36) through a DMA controller (30). Then, the sewing pattern graphic is displayed on the CRT (26) by the CRT control circuit (46). This allows the operator to input data while confirming it by referring to the graphic display.
FIG. 7 shows one example of the sewing pattern for sewing a label to a shirt. The formation of sewing pattern data and operation of sewing based on the sewing pattern data will now be described in detail. A sewing start point P is specified on the tablet digitizer (10) by the cursor (12). Similarly, sewing points P.sub.1 P.sub.2 P.sub.3 . . . P.sub.23 P.sub.24 P.sub.25 are specified to form the sewing pattern data.
In this case, it happens that the points P.sub.1, P.sub.2, P.sub.3 are superimposed on the points P.sub.23, P.sub.24, P.sub.25 at the same position, respectively. This processing is necessary to give a neat finish to the sewed material, and is commonly practiced.
FIG. 8 is a flowchart showing the operation of forming the above-mentioned data. Upon turning on a switch of the cursor (12) in Step S1, the X and Y coordinate values of point P are read in Step S2. The read coordinate values are stored in the data memory RAM (24) in Step S3, and further converted into sewing data for the sewing machine in Step S4 before being stored in the data memory RAM (24) again. The same processing is performed for the points P.sub.2, P.sub.3, P.sub.4, . . . P.sub.25.
FIG. 9 is an example of the content in the data memory RAM (24) in which the sewing pattern data shown in FIG. 7 is stored. In the figure, reference numerals X.sub.1, Y.sub.1, . . . X.sub.25, Y.sub.25 designate portions in which the data read by the digitizer (10) is stored. X.sub.1a, Y.sub.1a, . . . X.sub.25a, Y.sub.25a are the data after the data read by the digitizer have been converted into the sewing data for the sewing machine. The data before and after the conversion are formed in correspondence to needle position points P.sub.1, P.sub.2, . . . P.sub.25.
The sewing data forming device for the conventional sewing machine is constructed as described above, so that, in the case where the input operation is performed so as to superimpose the points P.sub.23, P.sub.24, P.sub.25 upon the points P.sub.1, P.sub.2, P.sub.3 as shown in FIG. 7, it is necessary .to instruct the cursor (12) to be positioned correctly on the points P.sub.1, P.sub.2, P.sub.3 which have already been inputted. However, it is extremely difficult to coincide the position data of the points P.sub.23, P.sub.24, P.sub.25 with points P.sub.1, P.sub.2, P.sub.3 due to the fact that the size of the points P.sub.1, P.sub.2, P.sub.3 is small or that the manual operation entails imprecision.